There is an increasing use of multi-media transmissions over cellular CDMA networks. However, a CDMA cellular network is by its very nature interferences limited. The layering of each signal across the available bandwidth increases the interference and affects the overall bandwidth utilization.
Attempts have been made in the past to limit the amount of interference by limiting the number of network users. This obviously affected the throughput of the network and also adversely affected new admissions to the network.
In a CDMA environment, in order to provide efficient bandwidth utilization the resources of the users that can be controlled are transmit power and data rates. The approach of power based admission policies has been to determine if a new potential user and existing users have sufficient power budgets to allow the new potential user to transmit at the requested data rate. Each user has an information bit energy to noise ratio that must be met in order to achieve desired quality of service requirements. It has been found, however, that the users cannot typically be allowed to transmit at their full transmit power capability since this adds unnecessary interference to the system, which in turn limits the number of possible users and the data throughput. Thus, the transmit power of each user has to be controlled to limit interference while at the same time allowing sufficient power to meet the users requirements
Besides power, the second user resource that can be controlled to maximize usage of the CDMA network is the data rate of the user. Two systems have been proposed for controlling the data rate. In a multi-code Code Division Multiple Access (MC-CDMA) system, each user operates at a fixed data rate using one or more codes to carry the information. The processing gain of each user is the same since the data rate is fixed. Processing gain is defined as the ratio between the signal baseband bandwidth and the spread spectrum bandwidth. Users attain higher data rates by using multiple codes simultaneously. In a Variable Gain Code Division Multiple Access (VG-CDMA) system, only one code is used by each user and the data rate is changed to meet the users data transfer requirements. The processing gain of the system changes inversely with the data rates. In both variable gain and multicode CDMA networks, provisions must be made to control the admission of new users in order for the system to operate at maximum throughput. The quality of services and Frame Error Rate of the user is dependent on the received bit energy to noise power ratio. Therefore, the admission strategy must ensure that the received bit energy to noise ratio for all user codes that are activated is above the required threshold.
A detailed mathematical analysis of the derivation of the algorithms for controlling the data rates and transmit power of users, so as to maximize throughput in cellular DS-CDMA networks is presented in the following references, which are hereby incorporated herein by reference in their entirety.    1) D. V. Ayyagari and A. Ephremides in Power Control Based Admissions Algorithms for Maximizing Throughput in DS-CDMA Networks with Multi-Media Traffic. IEEE-WCNC 1999, Sep. 25, 1999.    2) D. V. Ayyagari, Capacity and Admission Control in Multi-Media DS-CDMA Wireless Networks. Ph.D. Dissertation, University of Maryland, College Park, 1998.